Airrester

Abstract

An improved construction for an upwardly extending flare stack for the emergency venting to the atmosphere of large quantities of combustible gases, such improvement being for the purpose of preventing the inflow, and upstream flow of air, into the flare stack, comprising an annular obstruction means attached to the inner surface of the flare stack a short distance upstream of the downstream end of the stack.

What is claimed is: 
     
       1. In an upwardly extending flare stack for emergency venting to the atmosphere of large quantities of combustible gases, wherein during "standby" condition, when said combustible gases are not being vented, a small maintenance flow of purge gas is provided, for the purpose of maintaining said stack free of air, the improvement in construction of said flare stack to ensure air-free conditions, comprising; an annular ring plate mounted perpendicular to the axis of said stack inside said stack near the downstream end thereof, said annular ring plate providing an orifice of smaller cross-sectional area than said stack;   a thin-walled cylindrical tube of length at least equal to the diameter, sealably attached to the inside of said annular ring plate, a part of said tube extending upstream of said ring plate and part extending downstream;   whereby said maintenance flow of gas will flow through said orifice at a higher circumferential flow rate than the circumferential flow rate at the inner surface of said stack to prevent the upstream flow of air along the inner surface of said stack.   
     
     
       2. The flare stack as in claim 1 in which the part extending upstream is greater than the part extending downstream.